Go to dafont.com and find a font you like.
Download the file.
unzip it (It usually opens in the wizard through the browser, if not, then double click the folder, the unzip wizard should come up)
Right click the font file (It usually has an icon that looks like an "O", two "T"s or an "A")
Click "Copy"

1. Press the 'Start' button.
2. Click 'Control Panel'
3. If, on the side, it says "Switch to Classic View" then leave it, go to the next step, if it says "Switch to category view" go to step 5
4. Press "Appearance and Themes"
5. Press Fonts. (On the category view, it's on the side, under "See also"
6. Paste your font into that directory.